This application is based upon, claims the benefit of priority of, and incorporates by reference, the contents of Japanese Patent Application No. 2002-117456 filed Apr. 19, 2002.
1. Field of the Invention
The present invention relates to a refrigerating cycle device for a vehicle and a controlling method thereof.
2. Description of the Related Art
A conventional refrigerating cycle device for a vehicle as disclosed by Japanese Patent Laid-Open Publication No. 2000-73810 is known. The refrigerating cycle device for a vehicle is installed in a vehicle having an engine capable of switching combustion methods between stratified combustion and homogeneous combustion. Additionally, the vehicle has a brake booster that is driven by negative pressure generated in an intake system and accumulated as brake negative pressure.
When the accumulated brake negative pressure is not large enough to activate the brake booster during stratified combustion operation of the engine, the intake air quantity of the engine is reduced, and the refrigerating cycle device for the vehicle is prevented from being driven. When the outdoor air temperature is high, the combustion method is switched from stratified combustion to homogeneous combustion, so that the air-conditioning can be continued without stopping the driving of the refrigerating cycle device of the vehicle.
In this way, the refrigerating cycle device of the vehicle is stopped during the stratified combustion operation in order to reduce the load on the vehicle engine and thus reduce the intake air quantity. This causes the throttle valve to move to the closing side, and the brake negative pressure necessary for driving the brake booster can be secured while the stratified combustion operation is continued.
When the refrigerating cycle device for a vehicle should not be stopped the vehicle engine switches the combustion method from stratified combustion to homogeneous combustion. This reduces the intake air quantity and thus secures the brake negative pressure necessary for driving the brake booster.
However, since the refrigerating cycle device for a vehicle is thus stopped in order to secure the necessary brake negative pressure, the air-conditioning capability could fall short. In addition, the switching between stratified combustion and homogeneous combustion could result in poor fuel economy.
The present invention is directed to a solution to the above-described problems. It is thus an object of the present invention to provide a refrigerating cycle device for a vehicle that is capable of preventing the air-conditioning capability from falling short while improving vehicle fuel economy, and a method of controlling such a device.
In order to achieve the above-described object, the following technical means is employed. A refrigerating cycle device for a vehicle according to a first aspect of the present invention is installed in a vehicle having a vehicle engine (11) capable of carrying out stratified combustion and a brake booster (11a). Negative pressure generated in an intake system of the engine (11) is accumulated as brake negative pressure (Pb). The brake booster is driven by the brake negative pressure (Pb).
The refrigerating cycle device has a variable displacement type compressor (2) that uses the vehicle engine (11) as a driving source and a control means (14) for controlling the operation of the compressor (2). Negative pressure detection means (19a) for detecting the brake negative pressure (Pb) is provided. In the stratified combustion operation and at the time of brake operation to cause the vehicle to stop, the control means (14) controls the volume in the compressor (2) so that the load on the compressor (2) is reduced by a prescribed amount when the brake negative pressure (Pb) detected by the negative pressure detection means (19a) is below a prescribed value (B1), and then the volume in the compressor (2) is controlled so that it gradually increases.
In this way, the load on the vehicle engine (11) is reduced for the reduced load on the compressor (2), and the intake air quantity is reduced. More specifically, the throttle valve (11b) is set to the closing side, so that the brake pressure (Pb) is secured to continue the stratified combustion operation. Then, the volume in the compressor (2) gradually increases, and the air-conditioning capability can be prevented from being inadequate.
According to a second aspect of the invention, the prescribed load amount (A) to be reduced from the load on the compressor (2) is determined based on the degree of how much lower the brake negative pressure (Pb) is than the prescribed value (B1). In this way, the stratified combustion operation can be continued, while the effect on the air-conditioning capability can be minimized.
According to a third aspect of the invention, the load on the compressor (2) is controlled as the operation torque, so that the brake negative pressure (Pb) can be secured in direct association with the combustion method of the engine (11). The operation torque of the compressor (2) can easily be controlled using detection signals for the discharge volume, the discharge pressure, the engine revolution number, and the like used for normal control of the refrigerating cycle device (1).
The fourth to sixth aspects of the invention are related to a method of controlling a refrigerating cycle device for a vehicle and its technical significance is essentially the same as the refrigerating cycle device for a vehicle according to the first to third aspects.
Note that the reference characters in the parentheses indicate the correspondence between these elements and the elements in the following description of embodiments.